Where is the best place to search for life beyond the Solar System?
Astronomers using telescopes at ESO’s observatories in Chile
have discovered three planets around a dim dwarf star just 40 light-years from Earth.
These worlds have sizes and temperatures similar to those of Venus and the Earth.
They may be the best targets so far found in the hunt for life elsewhere in the Universe.
This is the ESOcast!
Cutting-edge science and life behind the scenes at ESO, the European Southern Observatory.
New telescopes and more sophisticated instruments
have allowed astronomers to discover and study large numbers of planets around other stars —
known as exoplanets.
Now scientists are searching for planets where we could detect life in the near future –
if it exists.
Astronomers hope to find the characteristic signatures in the atmospheres of these planets
of molecules that could indicate the presence of life.
But there are billions of stars in our galaxy,
so how can they find the kind of planets they are looking for?
A type of tiny dim red star called an ultracool dwarf is a good place to look.
They are the only places where life could be detected on an Earth-sized exoplanet using our current technology.
The light from much brighter stars — like the Sun for example —
would swamp vital measurements of the atmospheres of any candidate planets.
An international team of astronomers has used the Belgian TRAPPIST telescope
to monitor the brightness of an ultracool dwarf star in the constellation of Aquarius,
which has been named TRAPPIST-1.
They found that it faded slightly at regular intervals,
indicating that three planets were passing between the star and the Earth —
events known as transits.
The host star TRAPPIST-1 is much cooler and redder than the Sun and barely larger than Jupiter.
Stars like this are very common in the Milky Way and they are very long-lived.
This is the first time that planets have been found around one of them.
Transits like these provide a surprising amount of information about the planet.
The team were able to tell that the three planets are very similar in size to the Earth
and that they orbit very close to their dim parent star.
But the really exciting result is that all three planets might have habitable regions on their surfaces.
This study has found the first Earth-like planets that are well suited for the detection of biological activity.
The next step is to make more detailed observations,
using the next generation of telescopes; such as ESO’s European Extremely Large Telescope
and the James Webb Space Telescope, scheduled for launch in 2018.
That will allow astronomers to study the atmospheres of planets like this,
and to search for molecules related to biological activity, like ozone, methane or water.
Ultracool dwarf stars are common — they account for around 15% of the stars near to the Sun.
So this discovery opens up a new direction for planet-hunting,
a direction that is taking us one step closer to the goal of finding evidence for some kind of life on distant worlds.
Transcription by ESO; translation by —